Human Vision is an information-processing task. The human eyes are capable of looking at what is where but the brain processes and generates a representation of this information in its profusion of color, form, motion and detail. The central vision (center of our retina) has the highest visual acuity and discriminative vision. Visual acuity decreases with distance from the fovea (the center of the retina) to the periphery. The combined field of view of our both eyes is approximately 180° with a 120° area of overlap (FIG. 7). In general, the periphery is a larger low resolution field and the central is a smaller high resolution field.
The central area or fovea subtends only for 2.5° of our visual field but our head movements coupled with rapid eye saccadic eye movements gives the impression that the combined field of view has a resolution similar to that of the foveal resolution (high resolution). The fovea uses also these saccadic eye movements to acquire peripheral targets. A large web page, fixated at its center, creates the illusion of being equally legible all over. It is only when we maintain our focus at the center of the web page and do not shift our eyes to the edge that we realize that the periphery is illegible. Our goal is to increase and maintain the quality of this large high resolution visual field by improving identification task of the peripheral (e.g., parcentral) vision.